CNS - Lecture 4 Flashcards
motor commands are generated in
higher brain centres
final common path: sensorimotor cortex
signals from the sensorimotor cortex descend to the
brainstem and spinal cord motor neurons which innervate muscle fibres
How are output commands formed in the sensorimotor cortex and where are they sent
sensory input is combined with input from other parts of the brain to form output commands to the brainstem, basal ganglia, and the cerebellum.
where does the basal ganglia and the cerebellum send their outputs to
the thalamus and the brainstem
What are the Supraspinal centres involved in generating motor commands
sensorimotor cortex, brainstem, cerebellum, cerebral cortex, thalamus and basal ganglia
What are the necessary requirements for the operation of feedback control?
- sensory information
- mechanism of comparing sensory information to the desired state
** see document for feedback control mechanism
the two types of muscle receptors signal changes in muscle _______ and in muscle ________
- length
- force
Sensory receptor that signal changes in muscle length is called
muscle spindle
where are muscle spindles located
parallel with the force-producing muscle fibers inside the belly of the muscle
what are muscle spindles composed of
a connective tissue capsule, intrafusal muscle fibres and stretch receptors
sensory receptor that signal changes in muscle force are called
golgi tendon organs (tendon organs)
where are tendon organs located
tendinous fascicles at the ends of the muscle fibers
along with responding to muscle length changes, muscle spindle group 1A afferents also respond to
muscle or tendon vibration
The muscle spindle signals the length of a ______ muscle and the tendon organ signals
the force in an _______ muscle.
flexor
extensor
what are extrafusal muscle fibers and it’s function
main muscle fibers found outside the muscle spindle that product all the measurable force
2 types of motor neurons that innervate muscle
alpha motor neurons
gamma motor neurons
alpha motor neurons activate
the main muscle extrafusal fibers to contract
Gamma motor neurons activate
intrafusal muscle fibers
why are sensory afferents fired more rapidly when intrafusal muscle fibers are activated
when activated, it stretches the elastic non-contractile middle part of the muscle spindle where the sensory endings are located
what is the alpha-gamma coactivation theory
gamma motor neurons are coactivated with alpha motorneurons to keep muscle spindle afferents firing during muscle shortening
_______ _________ of a muscle causes Golgi tendon organ afferents to respond with
______ increases in their rate of firing
- passive stretching
- small
_______ of extrafusal muscle fibers causes the Golgi tendon organs to fire much more rapidly
contraction
The main role of gamma motor neurons is to
alter the sensitivity of muscle spindles to muscle length changes
during the stretch reflex: how do signals from the Golgi tendon organ (GTO) travel
signals travel to the the spinal cord
during the stretch reflex: what is the action of the golgi tendon organs
the GTO afferent from the extensor muscle activates an interneuron which inhibits the extensor motor neuron. Simultaneously it activates an interneuron which activates the antagonist flexor motor neuron
what is the flexor withdrawal reflex
withdrawal of a limb from a painful input
the function of feedback control is to
resist change and maintain a desired state
T/F during muscle stretch, the spinal cord reflexes act in the opposite manner as the stretch reflex
true
afferent signals from nociceptors in the foot cause reflex activation of the ________________ and reflex inhibition of the __________________
- flexor motor neurons
- extensor motor neurons
(results in lifting of leg away form stimulus)
Primary motor cortex is also called the
sensorimotor cortex
areas of the cerebral cortex that control movements of the extremities
pre-motor cortex, supplementary motor cortex, primary motor cortex, somatosensory cortex and parietal lobe association areas
primary sensory cortex is also known as
somatosensory cortex
what is most represented in the human somatotopic map of the primary motor cortex
hands and face representations
Neurons in the primary motor cortex can be activated by moving coil over different somatotopic representation areas to elicit movement in the body (mostly face and hands). This research tool is called
Transcranial magnetic stimulation (TMS)
The corticospinal tract (CTS)/pyramidal tract functions
- conveys signals from the sensorimotor cortex through the brainstem to the spinal cord
- CST neurons make monosynaptic connections with spinal alpha motorneurons, whose axons in turn activate muscles
- CST crosses to the contralateral side of the nervous system at the brainstem level
what forms the corticospinal tract
axons from neurons in the sensorimotor cortex
CST neurons are only ___ neuronal synapse away from muscles
one
stroke, cerebrovascular accident (CVA) or brain attack all result from damage to the
sensorimotor cortex
the inability to move the limb on the contralateral side of the body is called
hemiplegia
symptoms of hemiplegia
- weakness of extremities
- exaggerated stretch reflex
- muscle spasms
- speech deficits
- attentional deficits
speech is controlled by most people in
the left side of the brain
what are the 2 main speech areas
- broca’s area
- wernicke’s area
broca’s area is responsible for:
and lesions of broca’s area result in:
- motor aspects of speech
- motor aphasia (slurring speech)
Wernicke’s area is responsible for:
Lesions result in:
- comprehension of language, association of visual, auditory and sensory input with words
- sensory aphasia and dyslexia
